1. Field
One or more embodiments described herein relate to a compressor.
2. Background
A hermetic compressor generally includes a motor for generating a driving force in an inner space of a hermetic case, and a compression part coupled to the motor for compressing a refrigerant. The hermetic compressors may be classified as a reciprocal type, a scroll type, a rotary type, a vibration type and the like according to a refrigerant compression mechanism. The reciprocal type, the scroll type and the rotary type use a rotational force of the motor, while the vibration type uses a reciprocal motion of the motor part.
Among those hermetic compressors, the motor of the hermetic compressor using the rotational force has a crank shaft to transfer the rotational force of the motor to the compression part. For example, the motor of the rotary type hermetic compressor (hereinafter, referred to as a rotary compressor) includes a stator fixed to the hermetic case, a rotor inserted in the stator with a predetermined gap therebetween to be rotatable by interaction with the stator, and a crank shaft coupled to the rotor to transfer the rotational force of the rotor to the compression part.
The compression part includes a cylinder, a rolling piston and a vane for compressing a refrigerant in the cylinder, and a plurality of bearing members for defining a compression space together with the cylinder and supporting the crank shaft. The bearing members are typically located at one side of the motor to support the crank shaft. However, as compressors becomes highly efficient in recent time, a technology of minimizing compressor vibration by installing bearings at both upper and lower ends of the crank shaft.
However, when the bearings are installed at the upper and lower ends of the crank shaft as shown in the related art rotary compressor, a diameter of the crank shaft should be short to reduce a frictional loss and improve efficiency of the compressor. If the diameter of the crank shaft becomes longer due to an increase in the capacity of the compressor, a bearing surface increases, which causes the frictional loss to be increased and the efficiency of the compressor to be lowered. Furthermore, if the diameter of the crank shaft is too short, the crank shaft may buckle or get bent to lower reliability of the compressor.